Fuel systems in modern internal combustion engines fueled by gasoline, particularly for use in the automotive market, employ gasoline direct injection (GDi) where fuel injectors are provided which inject fuel directly into combustion chambers of the internal combustion engine. In such systems employing GDi, fuel from a fuel tank is supplied under relatively low pressure by a low-pressure fuel pump which is typically an electric fuel pump located within the fuel tank. The low-pressure fuel pump supplies the fuel to a high-pressure fuel pump which typically includes a pumping plunger which is reciprocated by a camshaft of the internal combustion engine. Reciprocation of the pumping plunger further pressurizes the fuel in order to be supplied to fuel injectors which inject the fuel directly into the combustion chambers of the internal combustion engine. During operation, the internal combustion is subject to varying demands for output torque. In order to accommodate the varying output torque demands, the mass of fuel delivered by each stroke of the pumping plunger must also be varied. One strategy to vary the delivery of fuel by the high-pressure fuel pump is to use a digital inlet valve which allows a full charge of fuel to enter the pumping chamber during each intake stroke, however, the digital inlet valve may be allowed to remain open during a portion of a compression stroke of the pumping plunger to allow some fuel to spill back toward the source. When the digital inlet valve is closed during the remainder of the compression stroke, the fuel is pressurized and the pressurized fuel is supplied to the fuel injectors. Examples of such an arrangement are disclosed in U.S. Pat. No. 7,401,594 to Usui et al. and in U.S. Pat. No. 7,707,996 to Yamada et al.
Digital inlet valves commonly include a check valve which is selectively held open during a portion of the compression stroke by a solenoid assembly to determine the fuel charge that is supplied to the fuel injectors. The solenoid assembly includes a pole piece which is stationary and an armature which is moveable based on application of an electric current to a coil. When the coil is energized with electricity, the armature is attracted to the pole piece. Conversely, when the coil is not energized, a return spring urges the armature away from the pole piece. In order to affect the state of the check valve, a control rod is rigidly fixed to the armature such that when the coil is not energized, the control rod urges the check valve to be held in an open position. Conversely, when the coil is energized, the control rod is moved to allow the check valve to open and close as a check valve normally functions based on the differential pressure across the check valve. When the coil is either energized or de-energized and the armature and control rod combination changes position, noise is generated when the combination of the armature and the control rod reaches a travel stop. Since the armature and the control rod are rigidly fixed to each other, the noise generated is a function of the total mass of the armature and the control rod and the impact velocity of the armature and control rod combination when the combination reaches the travel stop.
What is needed is a fuel pump and inlet check valve which minimizes or eliminates one or more of the shortcomings as set forth above.